1. Field of the Invention
The present invention relates to a thin film transistor, a display device including the same, and a manufacturing method thereof.
2. Description of the Related Art
A display device such as a liquid crystal display (“LCD”), an organic light emitting diode display (“OLED display”), and an electrophoretic display include a plurality of pixels. Each pixel includes a pair of field generating electrodes and an optical active layer formed therebetween. The LCD includes a liquid crystal capacitor having a liquid crystal layer as the optical active layer formed between the field generating electrodes, and the OLED display includes an organic light emitting diode having an organic emission layer as the optical active layer between the field generating electrodes.
The conventional display device includes a switching element connected to one of the pair of the field generating electrodes to control electric signals, and the optical active layer converts the electric signals into optical signals, to thereby display images. The switching element receives data signals from a data line and transmits them to a pixel electrode according to a scanning signal from a gate line, and mainly uses a thin film transistor (“TFT”).
The field generating electrode, the switching element, the gate line, and the data line are formed on at least one of display panels.
The display device also includes a gate driver applying scanning signals to the gate line and a data driver applying data signals to the data line. The gate driver and data driver are also operated according to signals transmitted from a signal controller, and may be formed on the display panel along with the field generating electrodes and the switching element. These drivers include a plurality of active elements made of TFTs.
Further, the OLED display further includes a driving transistor to flow the current to the organic light emitting diode according to the data signal transmitted from the switching element as well as the switching element.
However, the TFT of the pixel and the TFT of the driver have different characteristics, and the switching transistor and the driving transistor require different characteristics in the OLED display. For example, some TFTs are required to have a high on/off current ratio (Ion/Ioff), and other TFTs are required to have high charge mobility.
However, these characteristics are traded off such that it is difficult for TFTs having the same structure to simultaneously satisfy these characteristics.
To form the various TFTs having the different characteristics on one display panel, TFTs having different structures may be manufactured through different processes and different apparatus, but the manufacturing process is complicated and the cost and time are required remarkably increased.